Water repellent abrasive



Patented Mar. 7, 1933 UNITED STATES PATENT OFFICE v RUPERT S. DANIELS, FNEWARK, NEW ERSEY, ASSIGNOR TO BAKELITE CORPORATION,

' OF NEW YORK, N. Y., A CORPORATION OF DELAWARE WATER REPELLENT ABRASIVENo Drawing.

This invention relates to abrasives for use in wet grinding and moreparticularly to porous abrasive or grinding wheels for use with waterunder conditions where the temperature of the water is apt to reach 100C.

Artificial abrasive wheels and other like implements are prepared fromabrasive grit and a binder. A binding medium in extensive use for thispurpose is the synthetic resinous material obtained, for example, in thecondensation of a phenol with formaldehyde or its equivalent or otheraldehydes, which is designated as a resinoid on account of itscharacteristic difference from the true resins in that it polymerizesupon heating to a form that is infusible and insoluble for all practicalpurposes. Such abrasive wheels are made more or less porous in orderthat they may be effective for free cutting and lose about 7 5 per centof their strength when run in hot or boiling water which is necessaryfor certain industrial purposes; as a consequence they are practicallyuseless under such conditions.

I have discovered that this loss in strength in the presence of hot orboiling water can be materially reduced or avoided without affecting thefree cutting action of a porous grinding wheel by the impregnation ofthe wheel with a substance which has a melting point above 100 C. andwhich is water repellent. In other words, I have found it to beessentialin preventing material loss in strength of the wh eel that theimpregnating material should not be caused to flow from the wheel or beleached out or otherwise affected by hot or boiling Water.

Very' suitable impregnating materials which satisfy these conditionsarethe waxlike higher chlorinated naphthalenes or mixtures thereof,which are substantially free from monoand dichlor-naphthalenes and havemelting points above 100 C. It is not enough, however, that themeltingpoint be high, for a pitch which remains after distillation ofchlorinated naphthalene up to 355 C. still contains enough material thatis soluble in boiling water so as to render it ineffective as a waterrepellent; on this ae- Application filed September 15, 1928. Serial No.306,292.

count the impregnating material must also be substantially insoluble inboiling water.

A mixture of tri-chlorand tetra-chlor naphthalenes having a meltingpoint of approximately 107 C. (found by melting and then allowing tocool to constant temperature) is generally suitable, provided it issubstantially free from dichlornaphthalene and other objectionableadmixtures though boiling Water seems to have a slight softening actionon the wax-like mass. A preferable mixture is one consisting largely ofpentachlornaphthalene which solidifies at about 126 G. and which is notaffected by boiling water. The removal of the dichlornaphthalene, whichis present in the various chlorinated naphthalene wax mixtures inobjectionable amounts, is necessary as otherwise the mixture tends tosoften and is not effective as a water repellent when in contact withboiling 70 water.

A procedure which is suitable for the im- I pre ation of abrasive wheelscomprises preparlng a bath of the impregnating wax at a temperatureabout 15 degrees above its melting point in a closed chamber, heating awheel to about 135 0., immersing it in the molten wax, and applying apartial vacuum corresponding to about 28 inches of mercury. The wheel isleft in the wax until bubbling ceases and then the temperature of thewax is lowered almost to its solidification point. As the wheel isremoved from the bath, it is passed in front of a cooling air currentwhereupon the wax immediately hardens so that there is no loss fromdrippage. Excess wax on the surface is then removed. Wheels soimpregnated have been found to increasefrom 12 to 17 per cent in weight.Other methods of impregnation known. to the art may be substituted, itbeing desirable that the voids existing in the porous wheel be lies,although the resinoid binder may be. Therefore, the impregnatingmaterials perform the additional function of protecting the resinoidbinder when alkaline solutions 5 are used in grinding operations. Inaddition the above mentioned chlornaphthalene compounds act aslubricants at the cutting points, thus increasing the etficiency of thewheel, and prevent filling of the pores with ground material. Thetemperature of the wheel when it is run in boiling water does not reachthat of the melting point of the impregnating material and consequentlythere is no flow of the impregnating material from the wheel.

While the above disclosure is more specifically directed to grindingwheels, the invention is also applicable to the manufacture of abrasivepaper and other abrasive implements. Moreover, it is evident that thisinvention is not limited to abrasives bonded by means of phenolresinoids, but that other suitable types of binders known in the art,such as for example the glycerol-phthalic anhydride resinoids, suitablesilicates, carbamid or thiocarbamid resinoids, cellulose esters, etc.,may be used so long as they can be manipulated to yield an implementwhich can be impregnated.

I claim:

1. An abrasive implement for wet grinding having a porous structureprepared from abrasive particles bonded with a resinoid and impregnatedwith chlorinated naphthalene which is substantially free from monoand--dichlornaphthalenes.

2. An abrasive implement for wet grinding having a porous structureprepared from abrasive particles bonded 'wzlth a phenolformaldehyderesinoid and impregnated with 40 chlorinated naphthalene comprisinglargely pentachlornaphthalene and substantially free i from monoanddichlornaphthalenes.

In testimony whereof, I aflix my signature RUPERT S. DANIELS

